Mesenchymal stem cells derived from adipose tissue vs bone marrow: in vitro comparison of their tropism towards gliomas

Abstract

Introduction: Glioblastoma is the most common primary malignant brain tumor, and is refractory to surgical resection, radiation, and chemotherapy. Human mesenchymal stem cells (hMSC) may be harvested from bone marrow (BMSC) and adipose (AMSC) tissue. These cells are a promising avenue of investigation for the delivery of adjuvant therapies. Despite extensive research into putative mechanisms for the tumor tropism of MSCs, there remains no direct comparison of the efficacy and specificity of AMSC and BMSC tropism towards glioma.

Methods: Under an IRB-approved protocol, intraoperative human Adipose MSCs (hAMSCs) were established and characterized for cell surface markers of mesenchymal stem cell origin in conjunction with the potential for tri-lineage differentiation (adipogenic, chondrogenic, and osteogenic). Validated experimental hAMSCs were compared to commercially derived hBMSCs (Lonza) and hAMSCs (Invitrogen) for growth responsiveness and glioma tropism in response to glioma conditioned media obtained from primary glioma neurosphere cultures.

Results: Commercial and primary culture AMSCs and commercial BMSCs demonstrated no statistically significant difference in their migration towards glioma conditioned media in vitro. There was statistically significant difference in the proliferation rate of both commercial AMSCs and BMSCs as compared to primary culture AMSCs, suggesting primary cultures have a slower growth rate than commercially available cell lines.

Conclusions: Adipose- and bone marrow-derived mesenchymal stem cells have similar in vitro glioma tropism. Given the well-documented ability to harvest larger numbers of AMSCs under local anesthesia, adipose tissue may provide a more efficient source of MSCs for research and clinical applications, while minimizing patient morbidity during cell harvesting.

Figure 1. Stemness of the primary adipose-derived mesenchymal stem cell lines (AMSC), and the Invitrogen supplied commercial AMSC line, confirmed with FACS documenting the absence of hematopoetic surface antigens CD31/CD45 and the presence of cell adhesion markers CD73/CD90/CD105.

Percentage of each antigen was analyzed using Kaluza software and labeled in the responsive graph.

Figure 2. Stemness of primary AMSC lines demonstrated with differentiation along three mesenchymal lineages, Adipocyte (a, d , g), Osteocyte (b , e, h), and Chondrocyte (c , f, i), documented via lineage specific staining with Oil Red O, Alizarin Red, and Collagen II, respectively.

The details of the staining protocols are provided in the methods section. Scale bar, 50 µm.

Figure 3. Primary and commercial AMSCs and commercial BMSCs have similar tropism to glioma conditioned media in vitro, although there is notable variability in the tropism of the primary AMSC lines.

Analysis of individual cell line tumor tropism in a matrigel-coated insert Boyden chamber migration assay; migration for each line was normalized to the serum free media condition. Results are reported as mean ± S.E.M., n = 9. (* represents the statistically significant difference within groups and # represents the statistically significant difference between groups).

Figure 4. Growth curve documenting relative proliferation rates of commercial (Lonza) BMSC, commercial (Invitrogen) AMSC, and the two primary AMSC cell lines (671, 654).

The values shown are the mean of three replicates per cell line per time point, and the S.E.M (*:p<0.05).